Hi, I've got the 70-200 2.8 mk2 and the 70-300 f4-5.6L and I can't recommend the latter lens higher. It's the unsung hero in the Canon range. The I.S really is 4 stops, it's pretty light, built like a little tank, weather sealed, silent usm motor . As for image quality,it's as good as the 70-200. I really can't see any difference between the two. I use it on a variety of bodies and its equally at home on any full frame or crop. I do miss a bigger aperture on occasion though but not to often. The iso performance of your camera negates the smaller aperture for the most part. I guarantee you won't be disapointed.